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Brake fluid moisture content tester


Pete Lewis

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I went on to silicone when I recomissioned the car 18 months ago. Following the dire warnings around the news groups I replaced all the rubbers blew through the pipework with a modified foot pump and filled with dot5. In this case the car had been standing for 20ish years so the major overhaul was neccessary. No problems to date.

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On 08/01/2019 at 17:13, johny said:

I think what we need is some first hand info. Can anyone who's actually changed over to silicone without replacing all the system seals give us some feedback please?

Yes, the seals lost there form. It was as if there was air in the system as the seals had become soft. That was after about a year, not straight away.  Changed the seals and the system remained sound after that for many years.

Dave

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There is, of course, no guarantee that the new seals, plunger rubbers etc won't leak after 12/18 months, even after fitting new ones. This comes back to the numerous posts about the quality of spares, rubbers etc, which doesn't show up, good or bad until several years have past. Only then can you say "should have bought more of those", but then, too late. Even stuff in the same branded box cannot be trusted either due to counterfitting, different formula/manufacture or just a Friday afternoon batch!

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I got my seals etc from a well known supplier but even they won't know how good they are. Most of the parts are coming from the same importers, probably being repackaged so you have no idea how good they are. The days of well known branded parts coming direct from the manufacturer I fear is long gone. Look at the posts regarding shock absorbers. I read that well known respected brand names have been sold off so you don't know who's product is in the box.

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15 hours ago, johny said:

pay more to get better quality parts

Unfortunately all you ever seem to hear, or sometimes read on here, is 'I found it cheaper at .....', '...save a few quid....', '...why is the club shop more expensive?'  Reality is people do not seem to act on their own words.  For what it's worth, for anything I think 'critical' I tend to source it from somebody who actually uses that item/spare in their line of business; using Jigsaw Racing costs a bit more for just that re-assurance. 

Got that of my chest!

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but thats the point because you cant guarantee more expensive means better quality - I believe theres a very limited number of companies manufacturing spares for our cars now as theres just not sufficient demand so often theres just one supplying a particular item and you can pay a lot or a little for it but in the end get the same thing!

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Hi Folks,

                     fairly new here. I've read all the different forum articles on here over the last few weeks and it's pretty good.

However reading through this topic has had me scratching my head. A little cynicism comes across quite clearly.  Poor quality - surley not !!!

Most brake systems on our old cars are designed for DOT3. And that is what the various seals are spec'd to. 

Is DOT4 the same - nearly bit not quite. It has added Borate.for whatever purpose.

 

It's main failing is that it is a very good paint stripper.

DOT5 on the other hand will not lift your paint, But paint contaminated with DOT5 will be a devil to repaint.

Replacing DOT3/4 with DOT5 can have its problems. DOT5 aerates badly. There is a post on a  Harley biker forum give an account of off road bikes shaking the brake

reservoir badly and the brakes stopped working.

I appreciate that our cars do not shake that much and the small amount of fluid in the pipes would again not shake that much either.

 

What about the rubber?  Silicon is quite inert regarding the rubber seals. BUT DOT5 is not just silicon. It has a bunch of additives. One additive in particular actually makes the rubber swell. DOT3/4 also has this - but it is a different additive.  So do the different additives when mixed produce a problem. Yes and no.

There are reports all over the various forumnia that give both accounts. The majority state that it doesn't affect them.

So from new there should be no damage. I would suggest if changing to DOT5 replace ALL your rubber seals (don't forget the MC).

I am not aware of any brake component manufacturer for our parts that recommend DOT5 - I wonder why.

 

Your comment about poor quality is reasonable in my view. There are too many 'interesting' parts out there.

Not found any duff brake seals though.

If you are happy with your brakes then fine - but keep an eye on them.

 

Roger

 

 

 

 

 

 

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Roger,

I notice this your first post, welcome!  And don't be put off! We thrive on arguments and banter.

 

3 hours ago, RogerH said:

Most brake systems on our old cars are designed for DOT3. And that is what the various seals are spec'd to. 

But they were pure rubber, they ain't now so this doesn't really matter. Now they are composites which is why so many of the poorly made ones are failing.

 

3 hours ago, RogerH said:

It's main failing is that it is a very good paint stripper.

 

No, it's main failing is it's highly flammable. :o Petrol dripping on your exhaust is very unlikely to catch fire, DOT 3/4/5.1 is almost certain to catch fire. Probably the reason the US military have switched to silicone. 

 

3 hours ago, RogerH said:

BUT DOT5 is not just silicon. It has a bunch of additives. One additive in particular actually makes the rubber swell.

No, you're right,  it's not. :lol:  Dot5 is silicone, silicon is something else, that aside what is this additive called?  We do like some science on here along with opinions.

 

Doug

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Clearly a bit of thread drift from the original subject post, but my 2p’worth in any case.

I think experiences with silicon fluid can vary and may be dependent upon the material/quality of the seals fitted.

I have been using silicon in brake and clutch systems since rebuild in 2011 (for the usual reason of wanting to protect my new paint) and whilst this has been apparently problem-free in the brakes, I have seen fairly rapid degradation of the seals in the clutch system as evidenced by black staining in the master cylinder and accumulated black sludge in the slave after quite a short period. The clutch obviously works the seals a lot harder due to the increased range of travel in the cylinders and silicon is reported to have reduced lubrication properties compared to traditional glycol based fluid. I would also say I have been surprised at how soft rubbers exposed to silicon can become.

As part of a general overhaul of the clutch system (long story) I have had my original 1” Girling clutch slave cylinder stainless steel sleeved and re-rubbered by Past Parts. They use seals made in the UK by Nelson Stokes (Cornwall). Correspondence with Nelson Stokes produced the following helpful response in respect of use of silicon.

“Thank you for the enquiry I can’t comment on other suppliers but all our seals are compatible with silicon fluid but we do use two different materials one being SBR and the other EPDM. EPDM is the better material to use for this fluid but both are compatible”.

Clearly this is helpful but not definitive and I have decided to revert back to Dot 4 for the clutch only at this stage and will be happy to report results in due course. As a general comment, I too am of the mind-set that I would generally be happy to pay more for improved quality as I think many others are.

Ian F

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Hi Doug,

   thanks for the welcome.  I'm just visiting at the mo but have been considering joining the club. I'm already with two other clubs.

There are some many areas of concern with parts etc that it is easy to run riot with the keyboard - sorry.

 

Not sure when anything on a car was pure rubber but has not been for a long time.

However that is not the problem DOT3 keeps popping up as the standard. New materials can and do work well. Bad parts will always be bad parts. Buy from reputable suppliers.

Indeed Dot3/4/5.1 burns quite well. But thankfully most brake systems are simple in design and leaks are rare(ish).

Whereas 'waterless coolant' is also very flammable and leaks are common.  Driving these cars is dangerous.  The US military had the DOT5 developed so that their long stored vehicles would not absorb moisture over say a twenty year period. Turn the key and off you go.  BUT it is a compromise.

Haven't a clue what the additives are but there are a few.  If somebody knows please reveal all.

 

Hi Ian,

         I think the black staining is caused by the MC Ali body  (ali produces black fretting debris).  dot3/4 definitely produces black fluid very quickly.

Do your stainless sleeved MC give off black fluid.

 

Hi Pete,

             cheap parts are everywhere. Find a supplier that you get on with (I use both TRShop and Moss) a great deal. If there is a problem I report back to them.

I hope they take note. I feel they do.

 

 

Roger

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